The invention relates to a substituted barium-neodymium-titanium-perovskite, a dielectric, ceramic composition, a capacitor comprising a ceramic dielectric material and a microwave component, in particular a dielectric resonator, comprising a ceramic dielectric material.
The development of dielectric, ceramic materials is of increasing importance to the manufacture of electronic components, because the trend towards miniaturisation of said components is often limited only by the fact that the properties of the materials available are inadequate. Said inadequacies include, for example, the unsatisfactory reproducibility of the properties of dielectric, ceramic materials and the problematic optimization of the relevant parameters for certain fields of application.
The most important fields of application of dielectric, ceramic materials are formed by capacitive elements in electronic circuits, for example for the ceramic dielectric of capacitors and microwave components.
The most important properties for these applications are: a high dielectric constant .epsilon., a low dielectric loss factor tan .delta. and a temperature coefficient of the capacitance TC.sub.c .+-.0.
Customarily, dielectric ceramic compositions comprising barium oxide, titanium oxide, neodymium oxide as well as further binary oxides are used for these fields of application.
For example, European Patent Application EP 0 473 347 A1 discloses a dielectric ceramic composition which comprises predominantly barium oxide, titanium oxide, neodymium oxide, samarium oxide and bismuth oxide, and which is characterized by the following formula:
xBaO--yTiO2--z[(1-a--b)Nd.sub.2 O.sub.3 --aSm.sub.2 O.sub.3 --bBi.sub.2 O.sub.3 ], wherein PA1 xBaO--yTiO2--z[(1--a--b)Nd.sub.2 O.sub.3 --aSm.sub.2 O.sub.3 --bBi.sub.2 O.sub.3 ], wherein PA1 a.sub.1 +a.sub.2 + . . . +a.sub.n+1 =1, PA1 0,17&lt;a.sub.n+1 &lt;0,30, PA1 b.sub.1 +b.sub.2 + . . . +b.sub.n =1 and PA1 a.sub.1 *n.sup.1 +a.sub.2 *n.sup.2 + . . . +a.sub.n *n.sup.n +b.sub.1 *m.sup.1 +b.sub.2 *m .sup.2 + . . . +b.sub.m *m.sup.m =6. PA1 {Ba.sub.0.242 Sr.sub.0.02 Ca.sub.0.03 Nd.sub.0.232 Gd.sub.0.23 .box-solid..sub.0.246 }[Ti.sub.0.97 Nb.sub.0.03 ]O.sub.3.
0.10.ltoreq.x.ltoreq.0.20, PA2 0.60.ltoreq.y.ltoreq.0.75, PA2 0.10.ltoreq.z.ltoreq.0.24, PA2 x+y+z=1; PA2 0&lt;a.ltoreq.0.25 and PA2 0&lt;b.ltoreq.0.30. PA2 0.10.ltoreq.x.ltoreq.0.20, PA2 0.60.ltoreq.y.ltoreq.0.75, PA2 0.10.ltoreq.z.ltoreq.0.25, PA2 x+y+z=1; PA2 0&lt;a.ltoreq.0.30 PA2 0&lt;b.ltoreq.0.35 and
In accordance with an embodiment, the dielectric ceramic composition consists predominantly of barium oxide, titanium oxide, neodymium oxide, samarium oxide and bismuth oxide as the main components, and the dielectric ceramic composition is characterized by the following formula:
the total quantity of said main components comprises maximally 2.0% by weight of aluminium oxide.
In accordance with the exemplary embodiment, the relevant formulations are compounded and the material is calcinated at 1000.degree. C. and subsequently sintered at 1300.degree. C.-1400.degree. C.
In accordance with these or similar formulations, which are compounded from the starting oxides within very wide concentration ranges, in general a plurality of oxidic phases is formed. This leads to local variations in the microstructure, as a result of which it is very difficult to optimally adjust the properties of the relevant dielectric compositions, and the relevant parameters exhibit a high degree of dispersion when the manufacturing process is not continually accurately controlled.